1. Technical Field
The present invention relates to a decorative plastic molded article that can present an outer appearance of metallic color like without painting or coating the body of the molded article, and a manufacturing method thereof.
2. Description of the Related Art
Regarding decoration techniques, some methods as (1) or (2) below are known to impart an metallic color appearance to plastic molded articles which are used for cosmetic containers or their caps or the like,    (1) laminating metal layers on the surface of the plastic molded article by hot stamp or deposition,    (2) painting the surface of the plastic molded article which is injection molded with a metallic paint.
Hot stamp is a technique of heating a carrier film, on which metallic thin films of aluminum or the like are laminated, pressing it to the surface of the plastic molded article, and peeling off the metallic thin films from the carrier film. Thereby, laminated metallic thin films are formed on the surface of the plastic molded article.
Deposition is a technique of depositing a metal vapor, obtained by evaporating a metal such as aluminum in a vacuum container, to the surface of the plastic molded article. Thereby, a deposited film of metal is formed on the surface of the plastic molded article. Japanese Patent No. 4748470 discloses a decorative plastic molded article having deposited films composed of mainly two or more metals on the surface thereof.
The plastic molded article can present a metallic color appearance through the painting by the metallic painting film, hot stamp by the metallic thin film or deposition by the metallic deposited film, thereby endowing the product with high quality, and improving the value of the product.
However, painting, hot stamp and deposition are all secondary processing to the plastic molded article, so the number of the processes is increased, and the related cost is increased. That is, regarding the plastic molded article to be molded into a desired shape by injection molding or the like, a painting process is required for painting, a stamping process, in which the metallic thin film on the carrier film is transferred to the plastic molded article, is required for hot stamp, and a vacuum deposition process using a vacuum container is required for deposition. That is, for the painting, the hot stamp and the deposition, after the molding process for molding the plastic molded article into a desired shape, the decoration process (painting, stamping and vacuum deposition processes) for imparting the molded article a metallic color appearance is required, thus the increasing of the cost is inevitable.
Moreover, the decorative plastic molded article implemented with painting, hot stamp, and deposition consists of two elements i.e., the plastic molded article body and decorative layers (a painting film, a metallic thin film, and a metallic deposition film) laminated on the surface of the molded article body. The decorative layers and the molded article body are different in materials and thus will be affected by the temperature and humidity in the operating environment. The decorative layers will be peeled off or corroded due to the difference in thermal expansions between the molded article body and the decorative layers, or the moisture absorbing on the decorative layers, and the like. As a result, it turns into a degradation status where the color of the metal seems dim and pale, the commodity value drastically decreases, the aesthetic appearance cannot be maintained for a long time, and the durability becomes an issue.